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1.
Roads are one of the most widespread human‐caused habitat modifications that can increase wildlife mortality rates and alter behavior. Roads can act as barriers with variable permeability to movement and can increase distances wildlife travel to access habitats. Movement is energetically costly, and avoidance of roads could therefore impact an animal's energy budget. We tested whether reptiles avoid roads or road crossings and explored whether the energetic consequences of road avoidance decreased individual fitness. Using telemetry data from Blanding's turtles (Emydoidea blandingii; 11,658 locations of 286 turtles from 15 sites) and eastern massasaugas (Sistrurus catenatus; 1,868 locations of 49 snakes from 3 sites), we compared frequency of observed road crossings and use of road‐adjacent habitat by reptiles to expected frequencies based on simulated correlated random walks. Turtles and snakes did not avoid habitats near roads, but both species avoided road crossings. Compared with simulations, turtles made fewer crossings of paved roads with low speed limits and more crossings of paved roads with high speed limits. Snakes made fewer crossings of all road types than expected based on simulated paths. Turtles traveled longer daily distances when their home range contained roads, but the predicted energetic cost was negligible: substantially less than the cost of producing one egg. Snakes with roads in their home range did not travel further per day than snakes without roads in their home range. We found that turtles and snakes avoided crossing roads, but road avoidance is unlikely to impact fitness through energetic expenditures. Therefore, mortality from vehicle strikes remains the most significant impact of roads on reptile populations.  相似文献   

2.
Barriers that dissect continuous habitat, such as roads, initiate the process of habitat fragmentation and can filter or eliminate animal movement through otherwise pristine areas. A severe road barrier appears to exist in Banff National Park where the Trans‐Canada Highway (TCH) is known to impede the movement of some animals, but the effects of this barrier relative to natural barriers and continuous habitat have not been assessed. To compare animal movement in response to these three contexts, we translocated three species of murid rodents (meadow voles, Microtus pennsylvanicus, deer mice, Peromyscus maniculatus, and red‐backed voles, Clethrionomys gapperi) across the TCH (an artificial barrier), a forested strip in the median of the TCH (a natural barrier), in the adjacent highway verge (continuous grassy) and in nearby forest (continuous forested). We coated murids with fluorescent dye, released them at standardized distances, and followed the resulting trails to obtain detailed information on movement paths. Overall, individuals were 20% less successful crossing the TCH than natural (forested) barriers and 10% less successful crossing natural barriers than continuous habitat, but exhibited marked variation among species. Path tortuosity was negatively related to return success; more convoluted paths were associated with lower success across all treatments. Deer mice returned to their home‐ranges more often than the other two species, perhaps because of their generalist habitat preferences, nocturnal activities, or larger home ranges. In all treatments, the fractal dimensions of movement paths were very qualitatively similar to those observed for return success and tortuosity, indicating that the responses of these species were not influenced by spatial scale. Together, our results suggest that (a) murid species differ in the movement limitation imposed by both natural and artificial barriers, perhaps as a consequence of differences in habitat preferences and activity patterns, and (b) murid responses to a road barrier are only moderately different from responses to the natural barrier of a forest edge in the context of translocation experiments.  相似文献   

3.
Medical records from 694 reptiles admitted to the Wildlife Center of Virginia (WCV; Waynesboro, Virginia, USA) from 1991 to 2000 were reviewed to determine causes of morbidity and mortality. Eighteen species were represented but the majority of cases were four species; eastern box turtle (Terrapene carolina) (66%), eastern painted turtle (Chrysemys picta) (11%), common snapping turtle (Chelydra serpentina) (10%), and rat snake (Elaphe sp.) (6%). There was a significant increase in reptile cases during the study period both in absolute number and in proportion to the total caseload. Trauma (74%) was the most frequent cause of morbidity and mortality followed by unknown or undetermined (13%), aural abscessation (7%), infectious diseases (2%), and one nutritional disorder (0.1%). In addition, 3% of the cases were healthy animals that had been removed from the wild and consequently brought to the WCV. Causes of morbidity and mortality differed between the four most numerous species. Impact with a motor vehicle was the most frequent cause of trauma for eastern box turtles, eastern painted turtles, and common snapping turtles; however, garden-equipment-related trauma was the most frequent cause for rat snakes. Aural abscessation was only seen in eastern box turtles. Eighty percent of cases occurred between May and September and 65% occurred within the five counties closest to the WCV. The majority of morbidity and mortality was the result of human activities. The expanding human population in Virginia likely will continue to have an impact on the health of wild reptiles.  相似文献   

4.
Roads and highways represent one of the most important anthropogenic impacts on natural areas and contribute to habitat fragmentation, because they are linear features that can inhibit animal movement, thereby causing barrier effects subdividing the populations adjacent to the roads. The paper examines to what extent a narrow (2-lane) and a wide (4-lane) highways represent barriers for two small mammal species: bank volesClethrionomys glareolus Schreber, 1780 and yellow-necked miceApodemus flavicollis Melchior, 1834, and whether displaced rodents are able to return across roads of different widths. The study was performed at four sites in the Czech Republic. The capture-mark-recapture method was used to determine crossing rates. At two sites, the animals captured close to the road were transferred to the other side and released, to compare return movements across the roads with the movements made by the non-transferred animals. We found that the narrow highway did not prevent movement of neither of the species, although voles crossed only after they had been transferred. Wide highways, on the other hand, completely prevened crossing of both species. While the narrow highways acted at individuals level, the wide highways affected the population subvision.  相似文献   

5.
1. Barriers to immigration, all else being equal, should in principle depress local abundance and reduce local species richness. These issues are particularly relevant to stream‐dwelling species when improperly designed road crossings act as barriers to migration with potential impacts on the viability of upstream populations. However, because abundance and richness are highly spatially and temporally heterogeneous and the relative importance of immigration on demography is uncertain, population‐ and community‐level effects can be difficult to detect. 2. In this study, we tested the effects of potential barriers to upstream movements on the local abundance and species richness of a diverse assemblage of resident stream fishes in the Monongahela National Forest, West Virginia, U.S.A. Fishes were sampled using simple standard techniques above‐ and below road crossings that were either likely or unlikely to be barriers to upstream fish movements (based on physical dimensions of the crossing). We predicted that abundance of resident fishes would be lower in the upstream sections of streams with predicted impassable barriers, that the strength of the effect would vary among species and that variable effects on abundance would translate into lower species richness. 3. Supporting these predictions, the statistical model that best accounted for variation in abundance and species richness included a significant interaction between location (upstream or downstream of crossing) and type (passable or impassable crossing). Stream sections located above predicated impassable culverts had fewer than half the number of species and less than half the total fish abundance, while stream sections above and below passable culverts had essentially equivalent richness and abundance. 4. Our results are consistent with the importance of immigration and population connectivity to local abundance and species richness of stream fishes. In turn, these results suggest that when measured at appropriate scales (multiple streams within catchments), with simple protocols amenable to use by management agencies, differences in local abundance and species richness may serve as indicators of the extent to which road crossings are barriers to fish movement and help determine whether road‐crossing improvements have restored connectivity to stream fish populations and communities.  相似文献   

6.
Roads affect wildlife in many direct and indirect ways. For ungulates, roads may inhibit seasonal migration and may cause an effective loss of habitat due to avoidance. On the other hand, roadsides and associated agricultural lands offer high quality forage that may attract ungulates and increase the frequency of car accidents. Mitigating actions require detailed knowledge on space use in relation to roads. Using data from 67 global positioning system (GPS)-marked red deer in Norway, we quantified 1) scale of avoidance of roads, 2) crossing frequency, and 3) selection of crossing sites. Red deer avoided roads only on a very local scale and only during daytime, with minor influence of variation in road size (traffic burden). Marked red deer crossed roads, on average, 2 times per day. Females crossed more frequently than males and crossings were most frequent during autumn and winter and during night. Deer selected forested crossing sites close to agricultural pastures, reflecting that roads are crossed most often on nightly feeding excursions. Our findings imply that red deer in our study area have adjusted to exploit feeding habitat close to roads at times of low traffic burden. The high frequency of crossings suggests a limited influence on seasonal migration patterns. The frequency at which red deer cross highways suggests that mitigation measures to reduce road mortality may be effective if targeted in the right areas. © 2012 The Wildlife Society.  相似文献   

7.
Efforts to reduce the negative impacts of roads on wildlife may be hindered if individuals within the population vary widely in their responses to roads and mitigation strategies ignore this variability. This knowledge is particularly important for medium-sized carnivores as they are vulnerable to road mortality, while also known to use available road passages (e.g., drainage culverts) for safely crossing highways. Our goal in this study was to assess whether this apparently contradictory pattern of high road-kill numbers associated with a regular use of road passages is attributable to the variation in behavioral responses toward the highway between individuals. We investigated the responses of seven radio-tracked stone martens (Martes foina) to a highway by measuring their utilization distribution, response turning angles and highway crossing patterns. We compared the observed responses to simulated movement parameterized by the observed space use and movement characteristics of each individual, but naïve to the presence of the highway. Our results suggested that martens demonstrate a diversity of responses to the highway, including attraction, indifference, or avoidance. Martens also varied in their highway crossing patterns, with some crossing repeatedly at the same location (often coincident with highway passages). We suspect that the response variability derives from the individual''s familiarity of the landscape, including their awareness of highway passage locations. Because of these variable yet potentially attributable responses, we support the use of exclusionary fencing to guide transient (e.g., dispersers) individuals to existing passages to reduce the road-kill risk.  相似文献   

8.
Animal personality can be defined as conspecific individuals consistently differing in behavioral tendencies. Personality is typically identified by behavioral repeatability, which occurs when within-individual variance is low relative to among-individual variance in the population. Intraspecific comparisons of behavioral repeatability in juveniles and adults within and across years are rare, but would be useful for testing hypotheses related to origins of animal personality and whether individuals exhibit stable or diverging behavior with ontogeny. To examine within- and across-year behavioral repeatability for eastern box turtles (Terrapene carolina), we assessed boldness (movement latency after brief confinement) of captive-born juveniles twice within three days when eight months old. We then repeated these tests for the same individuals one year later. Juveniles exhibited repeatable boldness within and across years. Although increasing body temperature was slightly associated with decreased movement latency, test year (1 or 2), or housing experience (being raised in an enriched or unenriched condition) had no effects on boldness. We also assessed across-year repeatability of boldness (head emergence from the shell after brief confinement) for wild adults at 1–3 year intervals. Adults also exhibited repeatable across-year boldness that was of similar magnitude to juveniles. We found no indication that sex class or whether adults had been radio-tracked influenced boldness. Our results suggest eastern box turtles demonstrate consistent individuality in boldness from an early age that is largely unaffected by temporal or environmental variation, and these behavioral differences can be maintained for multiple years in captivity and the wild, contrasting with theoretical expectations for personality development. These findings add to recent accumulating evidence demonstrating juvenile and adult box turtles exhibit multiple repeatable behaviors over the short- and long-term. We suggest this species is quickly gaining traction as a model organism for studying the proximate and ultimate causes of personality development within long-lived animals.  相似文献   

9.
Roads exert various effects of conservation concern. They cause road mortality of wildlife, change the behaviour of animals and lead to habitat fragmentation. Roads also have genetic effects, as they restrict animal movement and increase the functional isolation of populations. We first formulate theoretical expectations on the genetic effects of roads with respect to a decrease in genetic diversity and an increase in genetic differentiation or distance of populations or individuals. We then review the empirical evidence on the genetic effects of roads based on the available literature. We found that roads often, but not always, decrease the genetic diversity of affected populations due to reduced population size and genetic drift. Whether the reduction in genetic diversity influences the long-term fitness of affected populations is, however, not yet clear. Roads, especially fenced highways, also act as barriers to movement, migration and gene flow. Roads therefore often decrease functional connectivity and increase the genetic differentiation of populations or the genetic distance among individuals. Nevertheless, roads and highways rarely act as complete barriers as shown by genetic studies assessing contemporary migration across roads (by using assignment tests). Some studies also showed that road verges act as dispersal corridors for native and exotic plants and animals. Genetic methods are well suited to retrospectively trace such migration pathways. Most roads and highways have only recently been built. Although only few generations might thus have passed since road construction, our literature survey showed that many studies found negative effects of roads on genetic diversity and genetic differentiation in animal species, especially for larger mammals and amphibians. Roads may thus rapidly cause genetic effects. This result stresses the importance of defragmentation measures such as over- and underpasses or wildlife bridges across roads.  相似文献   

10.
Forest-dwelling carabid beetles that have no flight ability were studied using mark-recapture methods in late-June to mid-October 2007. This study was done to determine the effects of narrow roads in Nopporo Forest Park, Hokkaido on carabid beetle movement and habitat use. The investigation was conducted at four sites: one site was an abandoned grassy road with a width of 3.5 m, two sites were gravel roads with widths of 3.5 and 4.5 m, and another site was an asphalt-paved road with a width of 4.5 m. A total of 3,580 individuals from six species of carabid beetles were collected using dry pit-fall traps, and recapture rates ranged from 6.1 to 36.2%. All examined roads acted as barriers against the movement of Leptocarabus arboreus ishikarinus. All roads, except the abandoned grassy road, acted as a barrier against Carabus granulatus yezoensis movement. Forest–roadside verge comparisons demonstrated that some carabid beetles avoid even narrow roadside verges. Harmful effects increase with increasing road width and both paved roads and narrow roads negatively affect the movement of carabid beetles inhabiting the bordering forest. Therefore, forest specialist beetles are influenced by a barrier effect that starts at the forest road verge, and this barrier effect may be exacerbated by vehicular traffic. Therefore, these barrier effects on carabid beetles should be considered when planning and implementing road construction and maintenance in forests.  相似文献   

11.

Background

Understanding the ecological consequences of roads and developing ways to mitigate their negative effects has become an important goal for many conservation biologists. Most mitigation measures are based on road mortality and barrier effects data. However, studying fine-scale individual spatial responses in roaded landscapes may help develop more cohesive road planning strategies for wildlife conservation.

Methodology/Principal Findings

We investigated how individuals respond in their spatial behavior toward a highway and its traffic intensity by radio-tracking two common species particularly vulnerable to road mortality (barn owl Tyto alba and stone marten Martes foina). We addressed the following questions: 1) how highways affected home-range location and size in the immediate vicinity of these structures, 2) which road-related features influenced habitat selection, 3) what was the role of different road-related features on movement properties, and 4) which characteristics were associated with crossing events and road-kills. The main findings were: 1) if there was available habitat, barn owls and stone martens may not avoid highways and may even include highways within their home-ranges; 2) both species avoided using areas near the highway when traffic was high, but tended to move toward the highway when streams were in close proximity and where verges offered suitable habitat; and 3) barn owls tended to cross above-grade highway sections while stone martens tended to avoid crossing at leveled highway sections.

Conclusions

Mortality may be the main road-mediated mechanism that affects barn owl and stone marten populations. Fine-scale movements strongly indicated that a decrease in road mortality risk can be realized by reducing sources of attraction, and by increasing road permeability through measures that promote safe crossings.  相似文献   

12.
Abstract Roads often negatively affect terrestrial wildlife, via habitat loss or fragmentation, noise, and direct mortality. We studied moose (Alces alces) behavior relative to a road network, in an area with a history of moose-vehicle accidents, to determine when moose were crossing roadways or using areas near roads and to investigate if environmental factors were involved in this behavior. We tracked 47 adult moose with Global Positioning System collars in a study area crossed by highways and forest roads. We hypothesized that moose would avoid crossing roads but would make occasional visits to roadsides to feed on sodium-rich vegetation and avoid biting insects. Further, we expected moose avoidance to be greater for highways than forest roads. We recorded 196,710 movement segments but only observed 328 highway and 1,172 forest-road crossings (16 and 10 times lower than expected by chance). Moose usually avoided road proximity up to ≥500 m on each side but 20% of collared moose made visits to areas within 50 m of highways, which might have resulted from moose searching for sodium in vegetation and roadside salt pools. In fact, vegetation along highways had higher sodium concentrations and was browsed in similar proportions to vegetation in adjacent forest, despite moose avoidance of these zones. Moose, however, did not use areas near roads more during periods of biting insect abundance. Our results supported the hypothesis of scale-dependent selection by moose; avoidance of highways at a coarse scale may confer long-term benefits, whereas selection of highway corridors at finer scales may be part of a strategy to overcome short-term limiting factors such as sodium deficiency. We found a positive relationship between home-range size and the proportion of road axes they contained, suggesting that moose either compensated for habitat loss or made specific movements along highways to gather sodium. The presence of sodium along highways likely increases moose-vehicle accident risks. Removal of salt pools or use of a de-icing salt other than sodium chloride should render highway surroundings less attractive to moose.  相似文献   

13.
14.
Large-scale spatial planning requires careful use and presentation of spatial data as it provides a means for communication with local stakeholders and decision makers. This is especially true for endangered species, such as the badger (Meles meles) in the Netherlands. To effectively mitigate the badger's traffic mortality in an area, two types of tools are needed. The first one estimates the probability of a successful road crossing for individual animals. The second tool is GIS-based and not only models the movement patterns of animals but also estimates an animal's daily number of road crossings. With data on population size as well as on road and traffic characteristics, a combination of both tools provides a measure of the mortality risk roads pose to wildlife in an area. Such estimations proved to be invaluable in a planning process with local inhabitants in the municipality of Brummen (the Netherlands), where ecological as well as safety problems appear. Our study demonstrates the applicability of GIS tools in balancing ecological consequences of road network options with a different distribution of traffic flows over the area in spatial planning and ecology.  相似文献   

15.
Selective logging is driving the proliferation of roads throughout tropical rain forests, particularly narrow, unpaved logging roads. However, little is known about the extent of road edge effects or their influence on the movements of tropical understory animal species. Here, we used forest rats to address the following questions: (a) Does the occupancy of rats differ from road edges to forest interior within logged forests? (b) Do roads inhibit the movements of rats within these forests? We established trapping grids along a road edge‐to‐forest interior gradient at four roads and in three control sites within a logged forest in Sabah, Malaysia. To quantify the probability of road crossing, rats were captured, translocated across a road, and then recaptured on subsequent nights. We caught 216 individuals of eight species on 3,024 trap nights. Rat occupancy did not differ across the gradient from road edge to interior, and 48 percent of the 105 translocated individuals crossed the roads and were recaptured. This proportion was not significantly different from that of rats returning in control sites (38% of 60 individuals), suggesting that small roads were not barriers to rat movements within logged forests. Subadults were significantly more likely to return from translocation than adults in both road and control sites. Our results are encouraging for the ecology of small mammal communities in heavily logged forests, because small logging roads do not restrict the movements of rats and therefore are unlikely to create an edge effect or influence habitat selection.  相似文献   

16.
Eastern box turtle (Terrapene carolina carolina) populations are in decline, likely due to anthropogenic forces and disease, necessitating hematologic and biochemical data from healthy individuals for evaluation of wild populations. We repeatedly sampled 21 free-ranging eastern box turtles from May to September 2009 in the spring, summer, and fall to establish temporal hematologic and biochemical reference intervals. Packed cell volume, aspartate aminotransferase, and potassium levels declined significantly as the active season progressed. High levels of albumin, globulin, and calcium coincided with the presence of eggs in females. These reference intervals should provide baseline data for the clinical evaluation of wild box turtles presented for veterinary care or for studies of wild populations.  相似文献   

17.
Roadways pose serious threats to animal populations. The installation of roadway mitigation measures is becoming increasingly common, yet studies that rigorously evaluate the effectiveness of these conservation tools remain rare. A highway expansion project in Ontario, Canada included exclusion fencing and ecopassages as mitigation measures designed to offset detrimental effects to one of the most imperial groups of vertebrates, reptiles. Taking a multispecies approach, we used a Before-After-Control-Impact study design to compare reptile abundance on the highway before and after mitigation at an Impact site and a Control site from 1 May to 31 August in 2012 and 2013. During this time, radio telemetry, wildlife cameras, and an automated PIT-tag reading system were used to monitor reptile movements and use of ecopassages. Additionally, a willingness to utilize experiment was conducted to quantify turtle behavioral responses to ecopassages. We found no difference in abundance of turtles on the road between the un-mitigated and mitigated highways, and an increase in the percentage of both snakes and turtles detected dead on the road post-mitigation, suggesting that the fencing was not effective. Although ecopassages were used by reptiles, the number of crossings through ecopassages was lower than road-surface crossings. Furthermore, turtle willingness to use ecopassages was lower than that reported in previous arena studies, suggesting that effectiveness of ecopassages may be compromised when alternative crossing options are available (e.g., through holes in exclusion structures). Our rigorous evaluation of reptile roadway mitigation demonstrated that when exclusion structures fail, the effectiveness of population connectivity structures is compromised. Our project emphasizes the need to design mitigation measures with the biology and behavior of the target species in mind, to implement mitigation designs in a rigorous fashion, and quantitatively evaluate road mitigation to ensure allow for adaptive management and optimization of these increasingly important conservation tools.  相似文献   

18.
Arboreal fauna living in tropical ecosystems may be particularly affected by roads given their dependency on forest cover and the high vulnerability of such ecosystems to changes. Over a period of 4 yr, we followed subgroups of spider monkeys living in a regenerating dry tropical forest with 8.2 km of roads within their home range. We aimed to understand whether roads shaped the home range of spider monkeys and which road features affected their movement. Only 18 percent (3 km) of the spider monkeys’ home range perimeter bordered with roads; these roads had greater habitat disparity between road sides than roads inside the home range. Although monkeys were reluctant to be close to roads, and roadside habitat contained low proportions of mature forest, spider monkeys crossed roads at 69 locations (7.5 crossings per kilometer). The main road characteristic affecting crossings was canopy opening size, with greater probability of crossing where canopy openings were smaller. Our findings support the importance of canopy opening size for road crossing of arboreal taxa, but they also indicate the relevant role roadside forest structure may have. Minimizing canopy opening size and forest disturbance along roads can facilitate the movement of arboreal fauna and preserve the important role of spider monkeys and other arboreal taxa in seed dispersal and thus the maintenance and regeneration of forest diversity.  相似文献   

19.
Road mortality is thought to be a leading cause of turtle population decline. However, empirical evidence of the direct negative effects of road mortality on turtle population abundance is lacking. The purpose of this study was to provide a strong test of the prediction that roads reduce turtle population abundance. While controlling for potentially confounding variables, we compared relative abundance of painted turtles (Chrysemys picta) in 20 ponds in Eastern Ontario, 10 as close as possible to high traffic roads (Road sites) and 10 as far as possible from any major roads (No Road sites). There was no significant effect of roads on painted turtle relative abundance. Furthermore, our data do not support other predictions of the road mortality hypothesis; we observed neither a higher relative frequency of males to females at Road sites than at No Road sites, nor a lower average body size of turtles at Road than at No Road sites. We speculate that, although roads can cause substantial adult mortality in turtles, other factors, such as release from predation on adults and/or nests close to roads counter the negative effect of road mortality in some populations. We suggest that road mitigation for painted turtles can be limited to locations where turtles are forced to migrate across high traffic roads due, for example, to destruction of local nesting habitat or seasonal drying of ponds. This conclusion should not be extrapolated to other species of turtles, where road mortality could have a larger population-level effect than on painted turtles.  相似文献   

20.
ABSTRACT Roads can affect the persistence of wildlife populations, through posing mortality risks and acting as barriers. In many countries, transportation agencies attempt to counterbalance these negative impacts. Road mortality is a major threat for European wildcats (Felis silvestris); therefore, we tested the effectiveness of a newly developed wildcat-specific fence in preventing wildcat mortality along a new motorway. We hypothesized that such a fenced motorway would at the same time be a significant barrier to wildcats and may at worst result in 2 isolated populations. We used radiotracking data of 12 wildcats, resulting in 13,000 fixes, to investigate individual movement behavior during and after construction of a new motorway in southwestern Germany. The motorway was fenced with the wildcat-specific fence and included crossing structures, not especially constructed for wildlife. Additionally we collected road kills on stretches of the same motorway with various types of fencing. A rate of 0.4 wildcat kills/km/year on the motorway, which was traveled by 10,000 vehicles/day and fenced with a regular wildlife fence, was reduced by 83% on stretches with wildcat-specific fencing. Of the available crossing structures, wildcats preferred open-span viaducts. Road underpasses were used but hold a mortality risk themselves. As opposed to our expectations, the fenced motorway (fenced with wildcat fence) posed only a moderate barrier to wildcats. Individuals were hindered in their daily routine and some stopped crossing completely but others continued crossing regularly. The adaptation of spatial and temporal behavior to traffic volume and location of crossing structures has an energetic cost. Hence, we suggest that only a small number of major roads can be tolerated within a wildcat's home range. To meet the demands of the European Habitats Directive, we recommend installing the wildcat fence in wildcat core areas along motorways to reduce wildcat mortality. We suggest that fences should incorporate safe crossing structures every 1.5-2.5 km. Our findings in terms of fencing design and crossing structures can be used by transportation agencies for an effective reduction of road mortality and barrier effect for carnivores.  相似文献   

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